Apple's iOS 4.3 has been jailbroken - good news for anyone who wants to install apps that haven't made it through - or can't pass - the Mac maker's iTunes App Store vetting process.
Better still, the jailbreak is 'untethered' - it doesn't require you to hook up your iPhone, iPad or iPod Touch to iTunes whenever you restart the …

Because

Apple wants iOS to be a closed platform so they can control the revenues produced. No problem with that per se except of course there are more open alternatives. For all the people choosing to jail break, perhaps they shouldn't have bought an iPhone in the first place.

I think I would be tempted to jailbreak an Apple TV device with iOS however, simply to flash the thing with XBMC.

Quite a lot

@Graham S, "So what's the difference between "jailbreaking" an iPhone and "rooting" an Android phone?"

Not much. Except of course most Android owners wouldn't need to root their phones because there are less restrictions on the kinds of apps you can install, and you can install apps from anywhere.

And even if you do want to root there are various tools available on the Marketplace for rooting / flashing devices and many others floating around. You are also able to choose the manufacturer of your handset if you believe one brand is less easy to root than others. Indeed most handsets appear only to have nominal root protection which seems more intended to stop people bricking their phones into an unrecoverable state.

So at a meta level, no there is little difference. At a practical level, neither Google nor handset manufacturers seem to especially care and there are plenty of handsets which let you do it easily.

don't mix security with tamper resistance

@ GrahamS

"So what's the difference between "jailbreaking" an iPhone and "rooting" an Android phone?"

"Jailbreaking" an iPhone is so you can actually install non-sanctioned apps, it it on other networks, access YOUR data as you choose, etc.

"Rooting" an Android phone is only useful if you want to remove MotoBlur or the like by installing a vanilla AndroidOS, upgrading the OS of an EoL phone (poor iPhone 3G, etc....), or gaining tethering (without paying for it...). Fortunately, these things are usually only the "geeks" of Droid-fandom as rooting your 'droid isn't necessary to install Apps from non-marketplace sources or to fetch data from it via USB....

There's benefits to either, but the sticking point is with the iPhone, it's necessary if your current wireless plan is not AT&T or Verizon (USA), but you want the new iThingy. (Most) carriers have a 'droid for their network made by a variety of manufacturers, which means if you don't like HTC Sense or MotoBlur, you don't have to get a smartphone with it. Not so with the iPhone. You get what you get and that's it. You can't even be ensured reasonable update lifetime apparently....something that fanbois have been decrying about 'droids for a while now. Guess it's true for both sides of the fence now.

Sort of...

They did this to a certain extent with a recent update to iBooks. It tries to execute unsigned code and, if successful, throws up a cryptic message about restoring iBooks and/or your device. Within hours of the jailbreak scene discovering this, there was a workaround on Cydia.

I can somewhat understand Apple's stance on this; jailbroken devices are considered to be a piracy risk, even though the majority of users jailbreak their devices for other reasons. And if publishers believe that jailbroken iDevices are a problem, whether that belief has a basis in fact or not, Apple needs to do what it can to keep them happy if their e-books platform is going to be a success.

On the other hand it has been decided by the US Courts that jailbreaking a device you own is not, in itself, illegal. So there's really only so much Apple can do to reduce the functionality of jailbroken devices, whose owners have done nothing wrong in the eyes of the law, without looking like the bad guys.

Some people have suggested that even the iBooks thing could have opened Apple up to potential legal issues, which is perhaps why they made the error message vague rather than emblazoning it with anti-jailbreak warnings.